Canadian fish farms spread disease to wild salmon. (Environmental Intelligence).

On the west coast of Canada, aquaculture is big business--farmed salmon is the province of British Columbia's largest legal export crop. Back in 1995, British Columbia banned new fish farms because of concerns about their effects on the province's six species of wild salmon. But a newly elected pro business government lifted the ban in 2002 and began a push to quadruple the province s salmon-farm output in a decade.

In recent months, 90 new salmon farms have been proposed. But severe outbreaks of diseases and parasites--which can spread easily between caged and wild fish--have put a crimp in the government's big plan. Scientists suspect that sea lice infestations among farmed fish led to last year's unprecedented 98-percent decline in pink salmon populations in the Broughton Archipelago off Vancouver Island. Roughly 3 million wild fish failed to migrate home to the area, which has the province's densest concentration of salmon farms. A year earlier, biologists had found fatal loads of sea lice covering young pink salmon swimming out to sea past the fish farms.

A governmental science advisory board has recommended that all 27 farms in the archipelago temporarily shut down during the pink salmon's out-migration season, but the province has only required 11 farms to lie fallow, in line with the B.C. Salmon Farmers Association's proposal. The remaining farms will add a pesticide to their fish feed in order to control sea lice outbreaks. "We are committed to operating salmon farms in a responsible manner without harm to wild salmon populations," says Ron Kilmury, the association's chairman. Leaders of many coastal tribes--whose cultures revolve around wild salmon--remain unconvinced. "Salmon-farming companies are not welcome here. They nearly wiped out the wild pink salmon and now they are refusing to help save them," says Brian Wadhams of the Musgamagw Tsawataineuk Tribal Council in the Broughton Archipelago.